The field of the invention is the production of nitriles and the present invention is particularly concerned with the liquid phase reaction of carboxylic acids or carboxylic alkylesters with ammonia in the presence of an iron catalyst.
The state of the art of nitrile production may be ascertained by reference to the Kirk-Othmer, "Encyclopedia of Chemical Technology", 2nd edition, Supplemental Volume (1971), pp. 590-603 under the section NITRILES, particularly pp. 592-593 and U.S. Pat. Nos. 1,991,955; 2,061,314; 2,177,619; 2,205,076; 2,493,637; 2,546,521; 2,555,606; 2,794,043; 2,808,426 and 2,993,926, the disclosures of which are incorporated herein.
Aliphatic nitriles are produced commercially and almost exclusively by reacting fatty acids or derivatives of these fatty acids with ammonia. In the gas phase production, the process is carried out with the vapors of the fatty acids or their derivatives, especially esters, passing together with ammonia at temperatures between 320.degree. and 600.degree. C. over dehydrating catalysts. The applicable catalysts include aluminum oxide, silica gel, oxides of thorium, titanium, molybdenum, tungsten and vanadium as disclosed in U.S. Pat. Nos. 1,991,955; 2,177,619; and 2,205,076; the article of J. A. Mitchell, E. E. Reid, published in the J. Amer. Chem. Soc. 53, 321 (1931) and the article in J. Appl. Chem USSR 45, 1824 (1972).
The high thermal loading on the input materials and the reaction products, and also as regards the apparatus required to carry out the reaction, can be reduced by operating in the liquid phase. However the liquid phase reaction still requires temperatures up to 350.degree. C. and requires a high pressure of reaction for low boiling point input materials as disclosed in U.S. Pat. Nos. 2,061,314; 2,546,521; and 2,555,606; and the article by R. L. Kenyon, D. V. Stingley, and H. P. Young, in Ind. Eng. Chem. 42, 202 (1950).
It is possible to further lower the temperature of reaction when operating in the liquid phase by using special catalysts. No reaction temperatures exceeding 315.degree. C. are required in the presence of the alcohol esters of titanium, zirconium or hafnium as disclosed in U.S. Pat. No. 2,993,926. When cobalt salt is used as the catalyst, the maximum temperature can be restricted to 290.degree. C. as disclosed in U.S. Pat. No. 2,493,637. The last two cited methods however suffer from the limitation of requiring the use of relatively costly catalysts which are reusable only to a limited degree.